RFR: 8004183: test/sun/management/jmxremote/LocalRMIServerSocketFactoryTest.java doesn't clean-up

[Peter Allwin]

Hello!

Looking for reviews of this fix where a jmxremote test left a worker thread running after completion. Fix is to flag the thread to finish and join before test method exit.

bug: https://bugs.openjdk.java.net/browse/JDK-8004183
cr: http://cr.openjdk.java.net/~allwin/8004183/webrev.00

Thanks!
/peter